Participant ID is a ByteArray; should be a string

[clehner]

In the Gadget API, wave.Participant.prototype.getId() returns a ByteArray, but it should return of a string.
For now it can be fixed in JavaScript with this line:

id = Array.prototype.map.call(id, function (x) { return String.fromCharCode(x); }).join("");

but it would be better if it was fixed in the C++ code.